The invention relates to a technique for outputting images based on image data, and in particular to a technique for outputting images by implementing a certain image process on image data to form dots at the appropriate density.
Image output devices for outputting images by the formation of dots on various types of output media such as printing media and liquid crystal screens are widely used as output devices in various types of image machines. In these image output devices, the images are handled while subdivided into small areas referred to as pixels, the dots being formed by the pixels. When the dots are formed with the pixels, it naturally cannot be made out whether or not dots have been formed by looking at the pixels one by one. However, when viewed in an area of a certain width, the crude density can be made out by the density of the dots that are formed, and the dot formation density can be varied to output images multiple tones. When, for example, black ink dots are formed on printing paper, areas where the dots are densely formed look black, whereas areas where the dots are sparsely formed look white. When bright spot dots are formed on liquid crystal screens, areas where the spots are densely formed look brighter, and areas where they are sparsely formed look dark. Images with multiple tones can thus be formed by suitably controlling the density with which dots are formed. Data for control the formation of dots so as to obtain suitable formation density are thus produced by implementing a certain image process on the image intended for output.
Recently there has been increasing demand for image output devices which output images of higher quality and greater size. Dividing images into finer pixels is an effective way to address the demand for higher image quality. Making pixels smaller allows the picture quality to be improved because the dots formed by the pixels do not stand out. The demand for larger images is addressed by increasing the number of pixels. The output image can be enlarged by enlarging the individual pixels, but as that would lead to lower picture quality, increasing the number of pixels is a more effective way to address demand for greater size.
Of course, when the number of pixels forming the image is increased, image processes take a longer time, making it difficult to output images rapidly. Techniques allowing image processes to be implemented more rapidly have thus been proposed (such as Japanese Unexamined Patent Application (Kokai) 2002-185789).
However, even though image processes can be implemented more rapidly, the transmission of image data or the transmission of processed image data takes more time, naturally limiting the ability to speed up image output.
Recently there has also been demand for directly outputting images by directly supplying data of images taken by digital cameras or the like to image output devices such as printing devices. In such cases, the image process cannot be carried out using an image processing device equipped with a high processing capacity such as what are referred to as personal computers. There is thus a need for a simple image process which could be handled by an image output device and/or image photographic device such as a digital camera.